Dry processing method and system for converter slag in copper smelting

ABSTRACT

The present invention provides a processing method for converting slag ejected from a converter in a copper smelting process to raw materials for iron manufacture. The processing method is for converter slag containing 1 mass % or more of Cu produced in a copper smelting process. The processing method comprises a step of charging the converter slag in a reduction furnace, and a step of conducting a heat reduction of a zinc content and a copper content contained in the slag and removing a reduced zinc by volatilization in the reduction furnace. The removal of the reduced zinc by volatilization is conducted in a condition in which an air fuel ratio of a volume of air blowing to an input of a reductant is controlled to 0.25 to 1.0.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a dry processing method and system forslag ejected from a converter in a copper smelting. In particular, thepresent invention relates to a dry processing method and system fortransferring slag ejected from a converter in a copper smelting to rawmaterials for iron manufacture.

BACKGROUND OF THE INVENTION

A general process of a copper smelting is as follows. An oxidationreaction of a copper concentrate which is a raw material is conducted ina flash smelting furnace, and about 68% copper grade of matte and aflash smelting furnace which contains iron oxide and silicate as a majorconstituent are produced and then separated. Next, the matte is fed intoa converter, and about 99% copper grade of blister copper and aconverter slag which contains silicic acid series iron oxide as a majorconstituent are produced and then separated. The blister copper is castto anode of higher purity in an anode furnace, and the anode is subjectto electrolytic refining and then electrolytic copper is produced.

On the other hand, with regard to the converter slag, slag floatationprocess, in which the converter slag is solidified and smashed and thena copper content is recovered by a flotation, is mainly employed(Journal of the Mining and Materials Processing Institute of Japan,“Mining and Materials Processing”, 1993. 12, Vol. 109, “nonferroussmelting issue”, page 954, 965; “Mining and Materials Processing”, 1997.12, Vol. 113, “recycling feature issue”, page 996, left column, lastparagraph). In the slag floatation process, slag copper concentrate ofhigh copper grade (about 25% Cu) and iron concentrate of low coppergrade (about 0.6% Cu) are separated, the copper concentrate can beprocessed repeatedly in the flash smelting furnace and the ironconcentrate can be used mainly as cement raw material.

Further, Japanese Patent Application Laid-open Publication No. 53-22115discloses a slag processing method in which copper oxide and Fe₃O₄contained in melt-state converter slag are reduced by adding a solidreductant such as coke and coal or a reductant such as gas and liquid tothe slag, and then 1% or less copper grade of slag and blister copperare produced.

A recovery method for copper content in slag, in which magnetite in theslag is reduced by adding powdered coal to melt-state converter slag,put into practical use at CALETONES smelter of Codelco in Chile (RolandoCampos and Luis Torres, CALETONES SMELTER:TWO DECADES OF TECHNOLOGICALIMPROVEMENTS, The Paul E. Queneau International Symposium, Ontario,CANADA (1993)).

-   (Patent documents 1) Japanese Patent Application Laid-open    Publication No. 53-22115-   (Nonpatent document 1) Journal of the Mining and Materials    Processing Institute of Japan, “Mining and Materials    Processing”, 1993. 12, Vol. 109, “nonferrous smelting issue”, page    954, 965-   (Nonpatent document 2) “Mining and Materials Processing”, 1997. 12,    Vol. 113, “recycling feature issue”, page 996, left column, last    paragraph-   (Nonpatent document 3) Rolando Campos and Luis Torres, CALETONES    SMELTER:TWO DECADES OF TECHNOLOGICAL IMPROVEMENTS, The Paul E.    Queneau International Symposium, Ontario, CANADA (1993)

SUMMARY OF THE INVENTION

Recently, Japanese cement market is on a shrinking trend and it isbecoming difficult to retain customers using the iron concentrateproduced by processing the converter slag with the slag floatationprocess disclosed in Patent document 1. Accordingly, a new applicationroute for the converter slag is required. On this point, the converterslag may be used for raw materials for iron manufacture because itcontains about 50 mass % of iron content. However, the converter slagcontains about 4 mass % of copper content and about 2 mass % of zinccontent. Accordingly, the copper grade and the zinc grade are too highfor using the converter slag as the raw materials for iron manufacture.Even the iron concentrate produced in the slag floatation processcontains about 0.6 mass % of copper content and about 2.5 mass % of zinccontent. Accordingly, the copper grade and the zinc grade are still toohigh for using the iron concentrate as the raw materials for ironmanufacture. It is desirable to maintain the copper content at 0.3 mass% or less and the zinc content at 1 mass % or less for use as the rawmaterials for iron manufacture. In the case of processing the converterslag by the methods of Nonpatent documents 1 to 3, the copper grade andthe zinc grade are still so high that the converter slag is unsuitablefor the raw materials for iron manufacture.

The present invention aims to provide a dry processing method and systemfor transforming slag ejected from a converter in a copper smelting toraw materials for iron manufacture.

The inventors have diligently studied to cope with the requirements, andeventually have found out a processing method for slag, in which a slagfuming process which is generally applied in zinc smelting is employed,an input of reductant in a reduction furnace is defined in apredetermined range, zinc is removed by volatilization from the slag,and on the other hand, copper is reduced, and then copper isprecipitated to separate blister copper from the slag in a reductionfurnace or in a settling furnace after moving the slag to the settlingfurnace arranged tandemly to the reduction furnace. The present methodallows the converter slag to convert to a slag in which the copper gradeand the zinc grade decrease to a utilizable level for the raw materialsfor iron manufacture. Further, the converter slag can be processedcontinuously by separating copper by precipitation not in the reductionfurnace but in the settling furnace separately.

Generally in the slag fuming process, melt-state slag is reduced byheating and metals such as Zn, Pb and As in the slag are volatilized,and for example, a reduction furnace in a lance for gas injecting or atuyere in a lower part of furnace is used. That is a process in whichthe metals in the slag are reduced and volatilized by jetting areductant (for example, propane gas or heavy oil) and combustion airfrom an end of the lance or the tuyere to the slag charged in thefurnace. The processed slag is discharged from a bottom part of furnaceand the volatilized metals are recovered from a top part of furnace.

The slag fuming process is generally used in a slag processing in zincsmelting. However, the process is not conventionally used in theconverter slag processing in the copper smelting like the presentinvention, and there is no such necessity. Accordingly, the presentinvention is highly characterized by applying the slag fuming process tothe converter slag processing in the copper smelting. Further, in anembodiment in which the slag extracted from the reduction furnace ismoved to the settling furnace and the reduced copper is separated byprecipitation and recovered there, the converter slag can be processedcontinuously and it is extremely advantageous for real operations.

Therefore, in one aspect, the present invention is a processing methodfor converter slag containing 1 mass % or more of Cu produced in acopper smelting process, comprising:

a step of charging the converter slag in a reduction furnace, and

a step of conducting a heat reduction of a zinc content and a coppercontent contained in the slag and removing a reduced zinc byvolatilization in the reduction furnace, and

wherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.

In another aspect, the present invention is a processing method forconverter slag containing 1 mass % or more of Cu produced in a coppersmelting process, comprising:

a step of charging the converter slag in a reduction furnace,

a step of conducting a heat reduction of a zinc content and a coppercontent contained in the slag and removing a reduced zinc byvolatilization in the reduction furnace, and

a step of separating a reduced copper by a precipitation from the slag,and

wherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.

In yet another aspect, the present invention is a processing method forconverter slag containing 1 mass % or more of Cu produced in a coppersmelting process, comprising:

a step of charging the converter slag in a reduction furnace,

a step of conducting a heat reduction of a zinc content and a coppercontent contained in the slag and removing a reduced zinc byvolatilization in the reduction furnace,

a step of transferring a reduced copper with the slag from the reductionfurnace to a settling furnace, and

a step of separating the reduced copper by a precipitation from the slagin the settling furnace, and

wherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.

In one embodiment, the present invention is the processing methodwherein the converter slag is held in a melt state, and the converterslag is charged in the reduction furnace from a holding furnace forcontrolling a supply of the converter slag to be supplied to thereduction furnace.

In another embodiment, the present invention is the processing methodfurther comprising a step of conducting a preliminary reduction of theconverter slag before supplying to the reduction furnace.

In yet another embodiment, the present invention is the processingmethod wherein the preliminary reduction is conducted in the holdingfurnace.

In yet another embodiment, the present invention is the processingmethod further comprising a step of crushing the slag after the step ofseparating the reduced copper by a precipitation from the slag.

In yet another embodiment, the present invention is the processingmethod wherein Fe₃O₄ contained in the slag is heat-reduced to FeO in thereduction furnace.

In yet another embodiment, the present invention is the processingmethod wherein the reductant is put in the slag flowing for thereduction furnace from the holding furnace.

In yet another embodiment, the present invention is the processingmethod wherein the reductant is put in the slag flowing for the holdingfurnace from the converter.

In yet another embodiment, the present invention is the processingmethod wherein the reductant used for the reduction of the slag in thereduction furnace is 1 to 10 mass % of coke to mass of the slag.

In yet another aspect, the present invention is a processing system forconverter slag containing 1 mass % or more of Cu produced in a coppersmelting process, comprising:

a reduction furnace in which a heat reduction of a zinc content and acopper content contained in the converter slag is conducted,

an exhaust means installed in the reduction furnace for removing thevolatilized reduced zinc,

a settling furnace for separating a reduced copper by a precipitationfrom the slag,

a transfer means for transferring the slag ejected from the reductionfurnace to the settling furnace, and

a discharge means for discharging the reduced copper separated by aprecipitation from the settling furnace, and

wherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.

In one embodiment, the present invention is the system furthercomprising a slag crush processing means and a transfer means fortransferring the slag ejected from the reduction furnace to the slagcrush processing means.

In yet another aspect, the present invention is a processing system forconverter slag containing 1 mass % or more of Cu produced in a coppersmelting process, comprising:

a reduction furnace in which a heat reduction of a zinc content and acopper content contained in the converter slag is conducted,

an exhaust means installed in the reduction furnace for removing thevolatilized reduced zinc,

a settling furnace for separating a reduced copper by a precipitationfrom the slag,

a transfer means for transferring the slag ejected from the reductionfurnace to the settling furnace, and

a discharge means for discharging the reduced copper separated by aprecipitation from the settling furnace, and

wherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.

In one embodiment, the present invention is the system furthercomprising a slag crush processing means and a transfer means fortransferring the slag ejected from the settling furnace to the slagcrush processing means.

In yet another embodiment, the present invention is the system furthercomprising:

a holding furnace for holding the converter slag in a melt state andcontrolling a supply of the converter slag to be supplied to thereduction furnace, and

a transfer means for transferring the converter slag ejected from theholding furnace to the reduction furnace.

In yet another embodiment, the present invention is the system furthercomprising a preliminary reduction furnace for conducting a preliminaryreduction of the converter slag before supplying to the reductionfurnace.

In yet another embodiment, the present invention is the system whereinthe holding furnace doubles as the preliminary reduction furnace.

ADVANTAGEOUS EFFECT OF THE INVENTION

The present invention allows the converter slag to continuously convertto slag in which the copper grade and the zinc grade decrease to autilizable level for the raw materials for iron manufacture. Further,the present invention allows copper recovery efficiency from the slag toincrease.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 indicates a continuous processing system for converter slag inone embodiment of the present invention.

FIG. 2 indicates a batch processing system for converter slag in oneembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the processing method and the system for theconverter slag of the present invention will be described with referentto FIGS. 1 and 2.

In general, in copper smelting process, a composition of slag ejectedfrom a converter is 50 to 60 mass % of iron content (mainly as Fe₃O₄ orFeO), 20 to 25 mass % of silicon content (mainly as SiO₂), 3 to 10 mass% of copper content (mainly as CuS, Cu₂O or CuO), 3 to 6 mass % of zinccontent (mainly as ZnO) and 1 to 3 mass % of aluminum content (mainly asAl₂O₃). In addition, 1 to 5 mass % of Cu is generally contained byitself.

Accordingly, in the present invention, “converter slag” indicates notonly slag actually ejected from the converter in copper smelting butalso slag having a similar composition with converter slag in coppersmelting. For example, about 3 to 5 mass % of raw minerals and Al₂O₃deriving from silicate minerals of solvent are contained in flashsmelting furnace slag in copper smelting. Accordingly, alumina (Al₂O₃)grade is too high for using the slag as raw materials for ironmanufacture. However, in the case that alumina grade is low in rawminerals, silicate minerals and flash smelter slag, the presentinvention can be applied.

Continuous Processing System

First, a continuous processing system for converter slag will bedescribed. Referring to FIG. 1, the slag flowing in receiving gutter 1from a converter (not shown) at melt state of 1200 to 1330° C. is guidedto holding furnace 2 with maintenance of the melt state. The holdingfurnace 2 may be guided to the slag in a condition of not being meltstate. For example, grained slag may be received in a hopper and thenthe slag may be guided to the holding furnace 2. The slag guided to theholding furnace 2 is held at melt state. The holding furnace 2 serves ascontroller of slag supply to the reduction furnace 4. For example, theholding furnace 2 supports a stable continuous operation of slagprocessing system by supplying constant flows of slag at all times tothe reduction furnace 4.

The slag coming out of the holding furnace 2 goes through slag gutter 3in melt state and are charged in the reduction furnace 4. Zinc content,copper content and other metal contents in the slag are reduced in thereduction furnace 4. Further, significant amount of magnetite (Fe₃O₄) isalso contained in the slag and viscosity of the slag can be lowered byreducing the magnetite to FeO. When the viscosity of the slag islowered, the reduced copper suspending in the slag is easy to separateby precipitation and copper recovery rate in next process increases.

Examples of reductant include, but are not limited to, carbonaceoussolid reductant such as coke and coal, gas reductant such as hydrogenand hydrocarbon (methane, ethane, propane, butane and the like), liquidreductant such as petroleum and heavy oil. Typically, LPG can be used.It is preferable to use upper blowing method in which the reductant isjetted with combustion air to the slag charged in the reduction furnace4 from an end of lance 5 set in from top part of furnace. This allowsreaction efficiency of the slag and the reductant to increase becausemelting slag in the reduction furnace 4 can be strongly stirred. The endof the lance 5 may be immersed in the slag. The tuyere installed in thebottom part of furnace can be used for supplying the reductant. Further,the reaction efficiency can be increased by increasing guide flow volumeof reductant and reduction time. That is, the zinc grade and the coppergrade in the slag can be lowered.

In the reduction furnace 4, for example, when propane is used as thereductant, the following reduction reaction occurs:

10Cu₂O+C₃H₈→20Cu+3CO₂+4H₂O

10ZnO+C₃H₈→10Zn+3CO₂+4H₂O

10Fe₃O₄+C₃H₈→30FeO+3CO₂+4H₂O

Examples of reductant to reduce the slag in the reduction furnace 4include, but are not limited to, heavy oil, LPG or coke. When coke isused, the input is preferably 1 to 10 mass % to the mass of the slag.

A volume of blowing to the input of the reductant to the reductionfurnace 4 is controlled to an air fuel ratio of 0.25 to 1.0. Since areduction reaction is an endothermic reaction, a temperature of the slagdecreases when the reaction proceeds. It is necessary to compensatingheat simultaneously with reduction so that the temperature of the slagmay not drop. However, when the air fuel ratio is below 0.25, thecompensating heat is short, the temperature of the slag drops, and thendeterioration of flowability of the slag and separability of the slagwith metals are caused. Further, for example, when the air fuel ratio is0.5, 50% of the reductant burn with air and then it is used for thecompensating heat, and the other 50% of the reductant is used forreduction of the slag. However, when the air fuel ratio is over 1.0, allof the reductant burn with air and its effect as reductant disappears.

When a reductant used in the reduction furnace 4 is coke, it may be putin the slag flowing from the holding furnace 2 to the reduction furnace.Specifically, it may be put in the slag gutter 3 shooting the slag fromthe holding furnace 2 to the reduction furnace 4. Further, it may be putin an out fall of the slag in the reduction furnace 4. This is becausereduction efficiency of coke is low when the coke is put in on the slagin the reduction furnace 4, and then the coke is preferably put in as itis involved in the slag.

The reduced zinc is volatilized from a slag phase and ejected with othervolatilized constituent or fine slag particles from gas duct 6 as slagfuming gas, and then guided to a plant for producing sulfuric acid. Onthe way to the gas duct to the plant for producing sulfuric acid, bagfilter 7 is installed, which can recover zinc. Further, cooling watermay be sprayed on the gas duct and a water-cooling tower (not shown) maybe installed to lower a temperature of exhaust gas. The reduced zinc maybe oxidized by air and the like on the way to the gas duct 6 and may berecovered by the bag filter 7 as zinc oxide. In general, lead is alsocontained in the slag fuming dust.

After the reduction reaction, the slag containing the reduced copper isejected from the reduction furnace 4 and then guided through solutiongutter 8 to settling furnace 9 with maintenance of the melt state. Thenthe reduced copper is separated by precipitation with difference inspecific gravity from the slag. The separation by precipitation isconducted not in the reduction furnace 4 but in the settling furnace 9installed separately, and then a continuous operation can be conducted.The efficiency of separation by precipitation can be increased and acopper grade in the slag can be lowered by lengthening a time for theseparation by precipitation. Conversely, recovery efficiency of coppercan be improved.

The reduced copper is discharged through the blister copper gutter 10after the separation by precipitation. A copper grade of the reducedcopper can be 40 to 80 mass % and the reduced copper can be returned tothe converter. On the other hand, the slag, which the reduced copper isseparated from, is transferred to the slag crush equipment 12 throughthe slag gutter 11, and then crushed to particle sizes that are easy touse. Examples of the crush equipment include, but are not limited to, awater crusher, crusher, a grinding mill, combinations thereof, and thelike. Considering a production of raw materials for iron manufacturefrom the reduced slag, it is necessary to lower a Zn grade because blastfurnace manufacturers have a restriction about the Zn grade. On theother hand, the Zn grade does not make any difference for electricfurnace manufacturers, and some of the manufacturers can use it as a rawmaterial when the Cu grade is lowered to 0.n % and its configuration isa massive form of 20 to 30 mm diameter. In this case, next of the stepin the settling furnace needs to be not a step in the water crushequipment but a step of coagulation to a massive form and a crushprocessing.

By going through the above processes, the copper grade in the slag canbe lowered to 0.3 mass % or less and the zinc grade in the slag can belowered to 1 mass % or less. Therefore, the slag processed by thepresent invention can be used as raw materials for iron manufacture.

In the present embodiment, the converter slag can be processedcontinuously. Accordingly, during a continuous operation of the system,the reduction reaction and the removal of the reduced zinc byvolatilization in the furnace, the separation of the reduced copper byprecipitation in the settling furnace and the crush processing for theslag in the slag crush equipment can be conducted simultaneously.

Batch Processing System

Next, a batch processing system for the converter slag will bedescribed. Referring to FIG. 2, the slag flowing in receiving gutter 1from a converter (not shown) at melt state of 1200 to 1330° C. ischarged in the reduction furnace 4 with maintenance of the melt state.Zinc content, copper content and other mental contents in the slag arereduced in the reduction furnace 4. Employable reductants and thereduction reaction in the reduction furnace 4 are the same as those ofthe continuous processing system. The recovery of the reduced zinc isalso the same as that of the continuous processing system.

After the reduction reaction, the reduced copper is separated byprecipitation in the reduction furnace 4. The reduced copper isdischarged through the blister copper gutter 10 after the separation byprecipitation. On the other hand, the slag, which the reduced copper isseparated from, is transferred to the slag crush equipment 12 throughthe slag gutter 11, and then crushed to particle sizes that are easy touse. The processed slag can be used as raw materials for ironmanufacture. The reduction furnace may be plurally installed inparallel.

In the present invention, a preliminary reduction furnace, whichconducts a preliminary reduction of the converter slag before supplyingto the reduction furnace 4, may be additionally installed. Thus, some ofthe copper oxide contained in the slag can be reduced and recovered byseparation by the preliminary reduction of the converter slag beforesupplying to the reduction furnace 4. Accordingly, usage of thereductant in the reduction furnace can be decreased and then theequipment can be reduced. That is, a load of the reduction furnace canbe reduced. The preliminary reduction is, but not limited to, preferablyconducted so that copper grade can be 2.5 mass % or less and zinc gradecan be 1.5 mass % or less in the converter slag. The preliminaryreduction may be conducted at 1200 to 1300° C. The holding furnace 2 maydouble as the preliminary reduction furnace. In this case, existingequipments can be used effectively and then production cost can befavorable. Further, by the preliminary reduction with the holdingfurnace 2, variability of compositions with each batch in the converterslag can be reduced and then the composition of the slag charged in thereduction furnace 4 can be stabilized. Accordingly, an input of thereductant to the reduction furnace 4 and a primary amount of combustibleair can be easily controlled. Examples of the reductant used in thepreliminary reduction include, but are not limited to, solid reductantssuch as coke and coal. Using such solid reductants, the preliminaryreduction can be conducted in the holding furnace 2. The reductant isput in to the holding furnace 2 in a manner such that coke or coal isput in to the melted slag, from the receiving gutter 1 used intransferring the slag from the converter, or in around an slag inputslot to the holding furnace 2. Thus, by putting in the reductant to themelted slag, the reductant is well stirred with the slag and then put into the holding furnace 2. Accordingly, it works well to the reductionreaction of the slag. Further, even though the reductant is put in largequantity, the reduction effect does not so good. Accordingly, forexample, the input of the reductant is preferably 1 to 10% to mass ofthe converter slag. In addition, “primary amount of combustible air”indicates an amount of air for burning the reductant to compensatingheat for those dropped in temperature by the reduction reaction of theslag.

EXAMPLES

Examples of the present invention will be described as follows, but thefollowing examples are intended to be illustrative and non-limiting.

Example 1

Slag ejected from a converter of copper smelting was processed on thefollowing conditions by a system described in FIG. 2.

converter slag: 10 ton

composition of converter slag: Shown at Table 1

input of heavy oil (reductant) to reduction furnace: 1438 L (basic unit144 L/ton-slag)

primary amount of combustible air: 5586 Nm³ (air fuel ratio 0.39)

slag reduction temperature: 1270° C.

composition of reduced slag: Shown at Table 2

settling time: 1 hour

TABLE 1 composition of converter slag (%) Cu Zn Ni Sn Pb 2.10 1.93 0.150.42 0.53

TABLE 2 composition of reduced slag (%) Cu Zn Ni Sn Pb <0.3 0.82 0.080.22 0.07

Example 2

Slag processing similar to Example 1, in which composition of slag wasdifferent from that of the converter slag of Example 1 and only the airratio w as changed, was conducted as Example 2.

converter slag: 7 ton

composition of converter slag: Shown at Table 3

input of heavy oil (reductant) to reduction furnace: 842 L (basic unit120 L/ton-slag)

primary amount of combustible air: 5539 Nm³ (air fuel ratio 0.66)

slag reduction temperature: 1270° C.

composition of reduced slag: Shown at Table 4

settling time: 1 hour

TABLE 3 composition of converter slag (%) Cu Zn Ni Sn Pb 3.68 2.49 0.250.44 0.45

TABLE 4 composition of reduced slag (%) Cu Zn Ni Sn Pb <0.3 0.64 0.130.18 0.06

Example 3

Slag ejected from a converter of copper smelting was processed on thefollowing conditions by a system described in FIG. 1. Further, apreliminary reduction was conducted in a holding furnace and then aconverter slag was charged in a reduction furnace.

converter slag: 165 kg

composition of converter slag: Shown at Table 5

input of carbon material (preliminary reductant) to holding furnace:2.2% to mass of converter slag

slag holding temperature: 1300° C.

composition of slag after holding: Shown at Table 6

input of heavy oil (reductant) to reduction furnace: 17 L (basic unit100 L/ton-slag)

primary amount of combustible air: 60 Nm³ (air fuel ratio 0.35)

slag reduction temperature: 1250° C.

composition of reduced slag: Shown at Table 7

settling time: 1 hour

TABLE 5 composition of converter slag (%) Cu Zn Ni Sn Pb 6.98 1.63 0.230.02 0.35

TABLE 6 composition of slag after holding (%) Cu Zn Ni Sn Pb 1.46 1.140.04 0.10 0.13

TABLE 7 composition of reduced slag (%) Cu Zn Ni Sn Pb <0.3 0.8 0.040.10 0.10

Reduced slags produced in Examples 1 to 3 are suitable for raw materials for iron manufacture for blast furnace manufacturers, and satisfyrecent demand for Zn grade to reduced slag from blast furnacemanufacturers. Especially, blast furnace manufacturers demand a rigorousspecification being a level of 0.n % of Zn grade. The reduced slags ofthe present Examples satisfy the required level.

EXPLANATION OF REFERENCE NUMBERS

-   1 receiving gutter-   2 holding furnace-   3 slag gutter-   4 reduction furnace-   5 lance-   6 gas duct-   7 bag filter-   8 solution gutter-   9 settling furnace-   10 blister copper gutter-   11 slag gutter-   12 slag crush equipment

1. A processing method for converter slag containing 1 mass % or more ofCu produced in a copper smelting process, comprising: a step of chargingthe converter slag in a reduction furnace, and a step of conducting aheat reduction of a zinc content and a copper content contained in theslag and removing a reduced zinc by volatilization in the reductionfurnace, and wherein the removal of the reduced zinc by volatilizationis conducted in a condition in which an air fuel ratio of a volume ofair blowing to an input of a reductant is controlled to 0.25 to 1.0. 2.A processing method for converter slag containing 1 mass % or more of Cuproduced in a copper smelting process, comprising: a step of chargingthe converter slag in a reduction furnace, a step of conducting a heatreduction of a zinc content and a copper content contained in the slagand removing a reduced zinc by volatilization in the reduction furnace,and a step of separating a reduced copper by a precipitation from theslag, and wherein the removal of the reduced zinc by volatilization isconducted in a condition in which an air fuel ratio of a volume of airblowing to an input of a reductant is controlled to 0.25 to 1.0.
 3. Aprocessing method for converter slag containing 1 mass % or more of Cuproduced in a copper smelting process, comprising: a step of chargingthe converter slag in a reduction furnace, a step of conducting a heatreduction of a zinc content and a copper content contained in the slagand removing a reduced zinc by volatilization in the reduction furnace,a step of transferring a reduced copper with the slag from the reductionfurnace to a settling furnace, and a step of separating the reducedcopper by a precipitation from the slag in the settling furnace, andwherein the removal of the reduced zinc by volatilization is conductedin a condition in which an air fuel ratio of a volume of air blowing toan input of a reductant is controlled to 0.25 to 1.0.
 4. The processingmethod of claim 1, wherein the converter slag is held in a melt state,and the converter slag is charged in the reduction furnace from aholding furnace for controlling a supply of the converter slag to besupplied to the reduction furnace.
 5. The processing method of claim 1,further comprising a step of conducting a preliminary reduction of theconverter slag before supplying to the reduction furnace.
 6. Theprocessing method of claim 5, wherein the preliminary reduction isconducted in the holding furnace.
 7. The processing method of claim 1,further comprising a step of crushing the slag after the step ofseparating the reduced copper by a precipitation from the slag.
 8. Theprocessing method of claim 1, wherein Fe₃O₄ contained in the slag isheat-reduced to FeO in the reduction furnace.
 9. The processing methodof claim 4, wherein the reductant is put in the slag flowing for thereduction furnace from the holding furnace.
 10. The processing method ofclaim 4, wherein the reductant is put in the slag flowing for theholding furnace from the converter.
 11. The processing method of claim1, wherein the reductant used for the reduction of the slag in thereduction furnace is 1 to 10 mass % of coke to mass of the slag.
 12. Aprocessing system for converter slag containing 1 mass % or more of Cuproduced in a copper smelting process, comprising: a reduction furnacein which a heat reduction of a zinc content and a copper contentcontained in the converter slag is conducted, an exhaust means installedin the reduction furnace for removing the volatilized reduced zinc, anda discharge means for discharging the reduced copper separated by aprecipitation from the reduction furnace, and wherein the removal of thereduced zinc by volatilization is conducted in a condition in which anair fuel ratio of a volume of air blowing to an input of a reductant iscontrolled to 0.25 to 1.0.
 13. The system of claim 12, furthercomprising a slag crush processing means and a transfer means fortransferring the slag ejected from the reduction furnace to the slagcrush processing means.
 14. A processing system for converter slagcontaining 1 mass % or more of Cu produced in a copper smelting process,comprising: a reduction furnace in which a heat reduction of a zinccontent and a copper content contained in the converter slag isconducted, an exhaust means installed in the reduction furnace forremoving the volatilized reduced zinc, a settling furnace for separatinga reduced copper by a precipitation from the slag, a transfer means fortransferring the slag ejected from the reduction furnace to the settlingfurnace, and a discharge means for discharging the reduced copperseparated by a precipitation from the settling furnace, and wherein theremoval of the reduced zinc by volatilization is conducted in acondition in which an air fuel ratio of a volume of air blowing to aninput of a reductant is controlled to 0.25 to 1.0.
 15. The system ofclaim 14, further comprising a slag crush processing means and atransfer means for transferring the slag ejected from the settlingfurnace to the slag crush processing means.
 16. The system of claim 12,further comprising: a holding furnace for holding the converter slag ina melt state and controlling a supply of the converter slag to besupplied to the reduction furnace, and a transfer means for transferringthe converter slag ejected from the holding furnace to the reductionfurnace.
 17. The system of claim 12, further comprising a preliminaryreduction furnace for conducting a preliminary reduction of theconverter slag before supplying to the reduction furnace.
 18. The systemof claim 17, wherein the holding furnace doubles as the preliminaryreduction furnace.
 19. The system of claim 14, further comprising: aholding furnace for holding the converter slag in a melt state andcontrolling a supply of the converter slag to be supplied to thereduction furnace, and a transfer means for transferring the converterslag ejected from the holding furnace to the reduction furnace.
 20. Thesystem of claim 14, further comprising a preliminary reduction furnacefor conducting a preliminary reduction of the converter slag beforesupplying to the reduction furnace.